Putting together a 5.3 and I have a set of LS1 heads and a set of 5.3 heads. Both stock. Just out of interest was wandering if anyone new which head would be a better choice on a slightly modified setup? Not looking to modify the heads.

 

You will lose power with the ls1 heads due to the larger Chambers...get a mild port and 3 angle valve job on your stock heads...........

 

I'd talk to Richard at WCCH and see what they have to offer...they used to have a StageI 5.3 head that tdrumm was running on his truck. IIRC, they were worth 20 or 30 HP on the dyno.

 

richard ported my 706's (5.3) and they flow just under 300cfm. infact im goin to use them on the 402 im building.

 

trans ams have 241s i think the 241s have biger valves than the 706s.if u mill them wont that be enough to compensate for the larger combustion chamber???

 

ls1 and 5.3 heads are the same. only difference is the ls1 chamber is a little bigger by 3 to 4cc. valves and ports are same. Attitude, your thinking bout the 243s. they have bigger ports and intake valve. Loudman, just look into a little port work on the 5.3 heads and it will rock.

 

Intake valves are larger as well..

 

Thanks. seems like the 5.3 heads sound like the better option. Now just throwing this out there as food for thought, since this is just a temporary backup, if i have the block bored to 3.90 would it be better to port the 5.3 heads or just use the LS1's.

sorry bout the hypotheticals just dont want to spend a lot of money on this set up but dont want to put together a complete turd.

comparing 852's to 241's if it make a difference

 

Incorrect kind Sir,
243's and 241/853's share 2.00/1.55 valves. 5.3 heads have 1.89/1.55" valves and a 61.1cc chamber. 241's have a better casting that supports higher flow than the 853's. 243's are the best factory LS1 style head to date with 64.5cc chamber and a more efficient chamber and port design that is nearly identical to the 317 (317 uses a 71cc chamber).

If you are thinking about doing a set of budget heads find some 243' for $450 on tech and get them milled .030" to get a chamber that is the same size as a stock 5.3 but promote much better flow. Or simply get your stockers ported by a "reputable" company. If you already have some 241's you can cut .035-.040 off of them to retain stock compression and add a little extra power.

 

would shaving the heads cause clearance issues with a high lift cam?